Summary/Abstract Amyotrophic lateral sclerosis (ALS) is the most common form of motor neuron degenerative disease and is characterized by a progressive loss of motor neurons in the spinal cord, brain stem and cerebral cortex. It can strike adults of any age, though is most common between the ages of 50-55 years. The molecular mechanisms that cause this disease are unclear and biomarkers specific for ALS are currently unknown. Our preliminary data using mass spectrometry based proteomics identified a panel of protein biomarkers from cerebrospinal fluid (CSF) with a high level of accuracy for diagnosing ALS near the time of clinical symptom onset. We propose to examine a much larger group of ALS and control subjects to further validate and identify protein based biomarkers for ALS. The goals of this proposal are to further explore the CSF proteome of ALS and control subjects to identify peptide and/or protein biomarkers for ALS. We will utilize liquid chromatography based mass spectrometry in a large unbiased screen for peptides that distinguish ALS from control subjects. We will then validate our findings in separate subject groups and generate a mass spectrometry based method to quantify specific peptides within the CSF and/or plasma that distinguish ALS from control subjects. We will then use this panel of biomarkers to distinguish sub- populations of ALS patients based on site of disease onset, age, gender, or rate of disease progression. These studies will generate novel biomarkers for ALS that could be used in future diagnostics for ALS and tested for their ability to monitor disease progression or drug efficacy in clinical trials.